Photosynthesis and Cellular
Respiration
How does your body get energy?
EATING!
When we eat,
our food is
broken down in
our bodies to
get energy out
of it.
What is energy?
the ability to do work
What does energy look like in your cells?
In cells,
energy is
stored in
the form of
ATP!
ATP = Adenosine Triphosphate
One big molecule that is made of 5
smaller molecules bonded together.
Adenine, ribose, and 3 phosphate groups
How does ATP give cells energy?
ATP breaks apart and releases its energy.
ENERGY!!!
We eat to get energy. How do the things
that we eat get energy?
The SUN!!!
The sun is the number
one source of energy.
Plants and algae use
energy from sunlight to
grow and make their own
energy.
How do they do this?
By a process called photosynthesis.
Photo-synthesis: “putting together with light”
+
+
So when a plant combines the energy
from sunlight with water and carbon
dioxide from the air, it gets energy!
The chemical reation of photosynthesis is…
6H2O + 6CO2 + light energy C6H12O6 + 6O2
Plants take in carbon dioxide and release
oxygen.
Leaves have special
parts called
chloroplasts!
Inside each
chloroplast is where
the photosynthesis
reaction takes place.
O O
Why don’t we get energy from sunlight when we
spend time outside??
Chloroplasts in plants
have a molecule called
chlorophyll that has
the ability to absorb
the energy from
sunlight.
Chlorophyll is a pigment
A pigment is a light absorbing molecule.
Chlorophyll is what
gives leaves their
green color.
If plants get their energy from sunlight, how do
they survive at night?
Photosynthesis has 2 parts, one that takes place in
light and one that takes place in dark.
Cellular Respiration!
Cellular respiration is a
chemical process in which
glucose molecules are
broken down to release
energy (ATP) for cellular
functions
What types of organisms undergo cellular
respiration?
Cellular respiration occurs in ALL living cells!
What happens to the food we eat?
1. We break our food down into small
molecules
2. We use the energy
stored in the bonds in
our food to make ATP
3. A small amount of the food
becomes waste
Where does cellular respiration
happen?
• The mitochondria or powerhouse of the
cell breaks down ATP energy for us, or
other plants and animals to use.
• You could say that cellular respiration
releases the energy that photosynthesis
creates for plants.
• In animals there is a very different process
to create energy, but the use of ATP is the
same!
Like photosynthesis, cellular respiration has a specific
chemical reaction that happens every time.
+
We breathe in oxygen and
get glucose from our food

We breathe out
carbon dioxide
O2 + C6H12O6  CO2 + H2O + Energy (ATP)
(reactants)
(products)
Photosynthesis
Equation
Main Function
Organelle it
occurs in?
Occurs in which
organisms?
Requirement of
Sunlight?
Cellular
Respiration
Photosynthesis
Equation
Main Function
Organelle it
occurs in?
Cellular
Respiration
CO2 + H2O + light -> C6H12O6 + O2
O2 +C6H12O6 -->
CO2 + H2O + ATP
Production of food.
Energy Capture.
Breakdown of food.
Energy release.
Chloroplasts
Mitochondria
(energy)
Occurs in which Occurs in plants,
protista (algae),
organisms?
Occurs in all living
organisms (plants
and animals).
Requirement of Can occur only in
presence of sunlight
Sunlight?
Sunlight not
required;
occurs at all times.
some bacteria.